1. Field of the Invention
The present invention relates to a feed roller of a roller unit for a recording medium, and more particularly to the feed roller of the roller unit for feeding the recording medium to an apparatus for reading, outputting, and processing information which has been recorded in the recording medium such as a CD, DVD, or the like.
2. Description of the Related Art
One example of a conventional roller unit for a recording medium including feed rollers of the type as described above is shown in FIGS. 3A and 3B. The feed rollers for the recording medium include roller shafts 2 which are supplied with rotating force for feeding a recording medium 1 such as CD, DVD, and rollers 3 formed of an elastic material such as rubber and having center bores through which the roller shafts 2 are inserted in a longitudinal direction to receive the rotating force from the roller shafts 2, thereby conducting the feed of the recording medium 1.
The rubber rollers 3 are tapered from both ends toward the center symmetrically in a longitudinal direction in order to prevent the recorded information recorded in the center of the recording medium from breakdown. Accordingly, the rubber rollers 3 are constructed in such a manner that their opposite end portions only are brought into contact with the recording medium 1 during the feed of the recording medium 1.
Operation of the conventional feed rollers for the recording medium constructed as above will be described below. When the roller shafts 2 are rotated, the rubber rollers 3 rotate following the rotation of the roller shafts 2 by friction between the roller shafts 2 and the rubber rollers 3, and thus, the recording medium 1 can be fed by the rotation of the rubber rollers.
In the event that the recording medium 1 is blocked by a stopper during the feed, a slippage occurs between the roller shafts 2 and the rubber rollers 3. This slippage will prevent the rubber rollers 3 from going on the rotation keeping contact with the recording medium 1, and thus, scratches on surfaces of the recording medium 1 can be avoided.
However, in the above described conventional feed rollers for the recording medium, the recording medium 1 cannot be fed because of the slippage between the roller shafts 2 and the rubber rollers 3, in case where feeding force of the rubber rollers 3 is smaller than frictional resistance between the recording medium 1 and the rubber rollers 3.
Conventionally, the feeding force required in the rubber rollers 3 has been obtained by inserting the roller shafts 2 into the center bores of the rubber rollers 3 with low pressure. In short, a force in a direction toward the roller shafts 2 has been imparted to the rubber rollers 3 by the low pressure insertion. This force will create friction between the roller shafts 2 and the rubber rollers 3, and as the result, the feeding force required in the rubber rollers 3 can be obtained.
However, the above described conventional feed rollers for the recording medium have had a problem that a diameter of the center bores of the rubber rollers 3 remarkably varies with temperature, and the feeding force of the rubber rollers 3 may also vary accordingly. For example, in case where the rubber rollers 3 are formed of the elastic material such as silicone rubber, the diameter of the center bores is increased by 0.03 mm at high temperature, and decreased by 0.03 mm at low temperature. Therefore, the feeding force is too weak at the high temperature, and too strong at the low temperature.
Further, there has been known another type of a feed roller for a recording medium as shown in FIG. 4. A compression spring 4 is provided at an intermediate position between two sections of the rubber roller 3. Both ends of the rubber roller 3 are held by holding members 5 which rotate in association with the roller shaft 2. Pressure fitting force is created on the rubber roller 3 in a longitudinal direction by elasticity of the compression spring 4, and this pressure fitting force will create friction between the holding members 5 and the rubber roller 3. This friction will make the feeding force of the rubber roller 3. However, in order to create the pressure fitting force in the longitudinal direction, it has been necessary that the above described conventional feed roller for the recording medium is provided with the compression spring 4 besides the rubber roller 3. This will increase components in number and incur a high production cost.
In view of the above, it is an object of the present invention to provide a feed roller for a recording medium which can obtain the required driving force only by a roller body without employing a compression spring, thus reducing number of components and production cost.
In order to solve the above described problems, there is provided, according to the present invention, a feed roller for a recording medium comprising a roller shaft supplied with rotating force for feeding the recording medium, a roller body made of an elastic material and provided with a center bore extending in a longitudinal direction through which the roller shaft is inserted, the roller body being adapted to receive the rotating force of the roller shaft thereby to conduct the feed of the recording medium, and a pair of holding members which rotate in association with the roller shaft and hold the roller body in a longitudinally compressed state by clamping opposite ends of the roller body.
According to the invention, the roller shaft is supplied with rotating force for feeding the recording medium. The roller body is provided with the center bore extending in the longitudinal direction through which the roller shaft is inserted. The pair of the holding members hold the roller body in the longitudinally compressed state by clamping the opposite ends of the roller body. Therefore, elasticity of the roller body itself will create pressure fitting force in the longitudinal direction. Because the roller body can obtain necessary driving force from the pressure fitting force, the compression spring need not be employed.
According to a second aspect of the invention, the roller body is separated into at least two sections. Therefore, because the holding members clamp and hold the roller body in the longitudinally compressed state, the divided sections apply forces with respect to each other thereby creating pressure fitting force in the roller body in the longitudinal direction. Thus, the roller body can obtain necessary driving force from the pressure fitting force, and the compression spring need not be employed.
According to a third aspect of the invention, feeding force of the roller body is set in such a manner that when the feed of the recording medium is interrupted, the roller body slips with respect to the roller shaft.
According to the third aspect of the invention, because the feeding force of the roller body is determined by the pressure fitting force occurring in the roller body in the longitudinal direction, that is, compressibility of the roller body, such feeding force that will make the roller body reliably slip with respect to the roller shaft when the feed of the recording medium is interrupted can be set.